Wellbores for the production of hydrocarbon fluid generally are provided with steel casings and/or liners to provide stability to the wellbore wall and to prevent undesired flow of fluid between the wellbore and the surrounding earth formation. A casing generally extends from surface into the wellbore, whereas a liner may extend only a lower portion of the wellbore. However in the present description the terms “casing” and “liner” are used interchangeably and without such intended difference.
In a conventional wellbore, the wellbore is drilled in sections whereby each section is drilled using a drill string that has to be lowered into the wellbore through a previously installed casing. In view thereof the wellbore and the subsequent casing sections decrease in diameter with depth. The production zone of the wellbore therefore has a relatively small diameter in comparison to the upper portion of the wellbore. In view thereof it has been proposed to drill a “mono diameter” wellbore whereby the casing or liner to be installed is radially expanded in the wellbore after lowering to the required depth. Subsequent wellbore sections may therefore be drilled at a diameter larger than in the conventional wellbore. If each casing section is expanded to the same diameter as the previous section, the wellbore diameter may remain substantially constant with depth.
U.S. 2010/0257013 A1 discloses a system including an expansion device for radially expanding and plastically deforming a tubular element whereby an actuator is coupled to the expansion device and whereby an anchor is coupled to the actuator. The anchor is activated to anchor the actuator to the tubular element while the actuator strokes in to expand a section of the tubular element. Thereafter the anchor is deactivated and pulled upward in order to allow starting expansion of a next section of the tubular element.
It is a drawback of the known system that, after arrival of the anchor at the top of the tubular element, a final upper portion of the tubular element cannot be expanded in this manner since the anchor no longer can be anchored to the tubular element at a higher position.